JPH03238052A - Preparation of catalyst for preparing methacrylic acid - Google Patents

Abstract

PURPOSE:To form a catalyst for preparing methacrylic acid containing P, Mo and V by adding ammonium carbonate to an aqueous solution of a raw material selected from oxide, carbonate and acetate and subsequently removing water to subject the residue to heat treatment. CONSTITUTION:At least one kind of a catalyst raw material selected from oxide, carbonate, acetate and hydroxide is added to water to prepare the aqueous solution or dispersion of the catalyst raw material. At least one kind of a compound selected from ammonium carbonate, ammonium bicarbonate, ammonium sulfate and ammonium bisulfate is added to the aqueous solution or dispersion. Subsequently, water is removed and the residue is heat-treated to form a multi-component type catalyst for preparing methacrylic acid containing P, Mo and V. This catalyst may not be supported but it is pref. to support the same on an inert carrier such as silica or alumina.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for preparing a catalyst used in the production of methacrylic acid by gas phase catalytic oxidation of methacrolein.

[Conventional technology]

Conventionally, when producing methacrylic acid by gas-phase catalytic oxidation of methacrolein, there were issues such as catalyst lifespan, suppression of side reactions,
From the standpoint of equipment cost, etc., it is advantageous to maintain a high yield at a low reaction temperature, but satisfactory results are not always obtained when catalysts prepared by conventional methods are used.

One of the reasons for this is thought to be insufficient control of the specific surface area and pore distribution of the catalyst, which is important for oxidation reactions. In order to improve these points, carboxylic acids and polyhydric alcohols were added during catalyst preparation (Japanese Patent Application Laid-open No.
136615), addition of alcohol and glycol (see JP-A-55-73347), addition of pyridines (JP-A-47-38591, JP-A-57-17).
1444), addition of quinolines (Japanese Unexamined Patent Publication No. 1444),
-209258), addition of ammonium ions (see JP-A-57-165040), etc., but the reaction results were not satisfactory, the catalyst activity decreased significantly over time, and the reaction temperature was too high. It has drawbacks such as being too expensive and requiring a complicated heat treatment method for activating the catalyst due to the use of an organic substance, so it is not necessarily sufficient as an industrial catalyst.

[Problem to be solved by the invention]

The present invention aims to provide a method for preparing a novel catalyst for the advantageous production of methacrylic acid from methacrolein.

[Means to solve the problem]

In order to improve the conventional catalyst preparation method, the present inventors conducted research focusing on the physical properties of the catalyst. As a result, they found that the catalyst is effective at a lower reaction temperature than when using a catalyst prepared by a conventional method, and that methacrylic We have discovered a new method for preparing a catalyst that provides a high yield of acid.

The present invention uses at least one raw material source selected from the group consisting of oxides, carbonates, acetates, and hydroxides as a raw material source for catalyst constituent elements during catalyst preparation, and uses an aqueous solution or an aqueous dispersion of the catalyst raw material. At least one compound selected from the group consisting of ammonium carbonate, ammonium hydrogen carbonate, ammonium sulfate, and ammonium hydrogen sulfate is added to the liquid, water is removed, and the residue is heat-treated.
A method for preparing a multicomponent catalyst for producing methacrylic acid containing phosphorus, molybdenum and vanadium.

The catalyst obtained by the method of the present invention has the general formula % (% formula %) (in the formula, P SMo5V , CLI, NH4 and 0
are each phosphorus, molybdenum, vanadium, copper, ammonium group, and oxygen, and X is at least one selected from the group consisting of potassium, rubidium, cesium, and thallium.
The seed element Y is at least one element selected from the group consisting of silver, magnesium, zinc, arsenic, germanium, silicon, tungsten, boron, bismuth, chromium, lanthanum, barium, antimony, iron, zirconium, tellurium, and cerium. The elements are shown as a, bSc, d, e.

f and h represent the atomic ratio of each element, g represents the number of ammonium group molecules, and when b=12, aO15-3, C=0.
01-3, d=0.01-2, e=0.01-2, f=
0 to 5, h is the number of oxygen atoms necessary to satisfy the number of ammonium group molecules, and g is preferably 0.01 to 2.

Molybdenum trichloride and molybdic acid are examples of the molybdenum raw material used for preparing the catalyst, and particularly good results are obtained when molybdenum trichloride is used. Raw material compounds for other catalyst constituent elements include oxides, carbonates,
Examples include acetates and/or hydroxides.

When carrying out the present invention, for example, molybdenum, vanadium, and phosphorus raw materials are dissolved or dispersed in water. After heating and sufficient reaction, other catalyst raw materials are added simultaneously or sequentially.

In the present invention, when adding other catalyst raw materials, ammonium carbonate, ammonium hydrogen carbonate, ammonium sulfate and/or ammonium hydrogen sulfate may be added, but in particular, after adding all other catalyst raw materials, dissolve in water. Good results are obtained when ammonium carbonate, ammonium hydrogen carbonate, ammonium sulfate and/or ammonium hydrogen sulfate are added.

The amount of ammonium carbonate, ammonium hydrogen carbonate, ammonium sulfate and/or ammonium hydrogen sulfate used is preferably 1 to 50% by weight, particularly 3 to 30% by weight, based on the total weight of the catalyst raw materials.

Next, water is removed from the mixture containing the catalyst raw material and ammonium carbonate, ammonium hydrogen carbonate, ammonium sulfate and/or ammonium hydrogen sulfate, and the residue is heat treated to obtain the desired catalyst. Heat treatment is for example 300~
It is preferable to carry out the process at a temperature of 430° C. under air circulation and/or under gas circulation with an oxygen concentration of 5% by volume or more.

Although the catalyst used in the method of the present invention is effective without a carrier, it is preferably supported on an inert carrier such as silica, alumina, silica-alumina, silicon carbide, or diluted with a carrier.

When producing methacrylic acid using the catalyst obtained according to the present invention, the concentration of methacrolein in the raw material gas can be varied within a wide range, but is preferably 1 to 20% by volume, especially 3%.
~10% is preferred. The raw material methacrolein may contain small amounts of impurities such as water and lower saturated aldehydes, but these impurities do not substantially affect the reaction.

As a catalyst source, it is economical to use air, but if necessary, air enriched with pure oxygen can also be used.

The oxygen concentration in the raw material gas is defined by the molar ratio to methacrolein, and this value is preferably 0.3 to 4, particularly 0.4 to 2.5.

The raw material gas may be diluted by adding an inert gas such as nitrogen, water vapor, or carbon dioxide gas. The reaction pressure is preferably from normal pressure to diffused pressure. The reaction temperature is 200-420℃, especially 230-400℃
°C is preferred. The reaction can be carried out in a fixed bed or in a fluidized bed.

The reaction rate of methacrolein and the selectivity of the produced methacrylic acid in the following Examples and Comparative Examples are defined as follows.

Reaction rate of methacrolein (%) Selectivity of methacrylic acid (%) In the following Examples and Comparative Examples, parts mean parts by weight, and analysis was performed by gas chromatography.

Example 1 100 parts of molybdic acid trioxide, 2.6 parts of vanadium pentoxide
and 6.7 parts of 85% phosphoric acid to 800 parts of pure water,
The mixture was heated to reflux for an hour. To this was added 12 parts of copper acetate, and the mixture was further heated under reflux for 3 hours. After refluxing, 11.2 parts of cesium bicarbonate dissolved in 100 parts of pure water were added, and further 5.6 parts of ammonium carbonate dissolved in 100 parts of pure water were added, and the mixture was evaporated to dryness while heating. The obtained solid material was dried at 120°C for 16 hours, then pressure molded and heated at 380°C under air circulation.
It was heat-treated for 5 hours. The composition of the components other than oxygen of the obtained catalyst (the same applies hereinafter) is PJo+ 2Vo, 5cLIo
, , cs+ (NHa) was 0.3.

This catalyst was packed into a reactor, and 5% methacrolein and 1% oxygen were added.
A mixed gas of 0% water vapor, 30% water vapor, and 55% nitrogen (volume %) was passed through the reactor at a reaction temperature of 285° C. and a contact time of 3.6 seconds. When the product was collected and analyzed by gas chromatography, the reaction rate for methacrolein was 84.1% and the selectivity for methacrylic acid was 83.8%.

Comparative Example 1 A catalyst with the same composition as in Example 1 was prepared without the addition of ammonium carbonate. Using this catalyst, the reaction temperature was changed to 290° C., and the reaction was carried out under the same conditions as in Example 1. The reaction rate of methacrolein was 80.0%, and the selectivity of methacrylic acid was 81.6%.

Example 2 Molybdenum dioxide 100 instead of ammonium carbonate
9.2 parts of ammonium hydrogen carbonate was added to the part, and potassium carbonate, silica sol, and arsenic acid were used, and the rest was as in Example 1.
According to the composition PIMO12VO, 5cuo, + to +
A catalyst of Sio, 3AS0.2(N)+4)0.2 was prepared.

When this catalyst was used and the reaction temperature was changed to 270°C and the other conditions were the same as in Example 1, the reaction rate of methacrolein was 84.3% and the selectivity of methacrylic acid was 86.6.
%Met.

Comparative Example 2 A catalyst with the same composition as in Example 2 was prepared without the addition of ammonium bicarbonate. Using this catalyst, the reaction temperature was increased to 280℃.
When the reaction was carried out under the same conditions as in Example 1 except that the temperature was changed to .degree. C., the reaction rate of methacrolein was 78.9% and the selectivity of methacrylic acid was 84.2%.

Example 3 Part of ammonium carbonate was changed to ammonium sulfate, and 2.8 parts of ammonium carbonate was added to 100 parts of molybdenum trioxide.
Rubidium acetate, cerium oxide and iron oxide were used, and the composition was P +, sMO + 2Vo, a according to Example 1.
cuo, JblCeo, +Feo, 2sbo,s
(NH4). , 4 catalyst was prepared. At this time, antimony dioxide was used as an antimony raw material source.

Using this catalyst, a reaction was carried out under the same conditions as in Example 1 except that the reaction temperature was changed to 270°C. The reaction rate of methacrolein was 89.6%, and the selectivity of methacrylic acid was 88.7%.
Met.

Comparative Example 3 A catalyst with the same composition as in Example 3 was prepared without the addition of ammonium carbonate and ammonium sulfate.

Using this catalyst, the reaction temperature was changed to 270°C, and the other conditions were the same as in Example 1. The reaction rate for methacrolein was 77.2%, and the selectivity for methacrylic acid was 87.0.
%Met.

Example 4 Part of the ammonium carbonate was replaced with 1 2 ammonium hydrogen sulfate, and a mixed solution of 2.8 parts of ammonium carbonate and 11.5 parts of ammonium hydrogen sulfate was added to 100 parts of molybdenum trioxide, and potassium carbonate and bicarbonate were added. Cesium and bismuth oxide were used, and the composition was P according to Example 1.
1.1M012VO, aCuo, Ja, tC8o, 5
A catalyst with B1o,2Sbo,t(NH4)0.4 was prepared. At this time, antimony penta'oxide was used as an antimony raw material source.

Using this catalyst, the reaction temperature was changed to 270°C, and the other conditions were the same as in Example 1. The reaction rate for methacrolein was 90.5%, and the selectivity for methacrylic acid was 88.7%.
Met.

Comparative Example 4 A catalyst with the same composition as in Example 4 was prepared without the addition of ammonium carbonate and ammonium hydrogen sulfate. Using this catalyst, the reaction temperature was changed to 290°C, and the other conditions were the same as in Example 1, and the reaction rate of methacrolein was 8.
The selectivity for methacrylic acid was 87.3%.

Examples 5-7 Each catalyst shown in Table 1 was prepared according to Example 1.

The part of added ammonium salt in the table is 10 parts of molybdenum trioxide.
Means parts by weight relative to 0 parts by weight.

A reaction was carried out in the same manner as in Example 1 except that these catalysts were used and the reaction temperature was changed. The results are also shown in Table 1.

3 4 Examples 8-10 Each catalyst shown in Table 2 was prepared according to Example 3.

The part of added ammonium salt in the table is 10 parts of molybdenum dioxide.
Means parts by weight to the nearest 0 parts by weight.

A reaction was carried out in the same manner as in Example 1 except that these catalysts were used and the reaction temperature was changed. The results are also shown in Table 2.

6 Procedural amendment (voluntary) flat bottom 2nd year may 10th

Claims (1)

[Claims] 1. Oxide as a raw material source for catalyst constituent elements during catalyst preparation;
At least one raw material source selected from the group consisting of carbonates, acetates, and hydroxides is used, and ammonium carbonate, ammonium hydrogen carbonate,
Phosphorus, characterized in that after adding at least one compound selected from the group consisting of ammonium sulfate and ammonium hydrogen sulfate, water is removed and the residue is heat treated.
A method for preparing a multicomponent catalyst for the production of methacrylic acid containing molybdenum and vanadium. 2. The catalyst for producing methacrylic acid has the general formula P_aMo_bV_cCu_dX_eY_f(NH_4
)_gO_h (wherein P, Mo, V, Cu, NH_4 and O are phosphorus, molybdenum, vanadium, copper,
ammonium group and oxygen, X is potassium, rubidium,
At least one element selected from the group consisting of cesium and thallium, Y is silver, magnesium, zinc, arsenic, germanium, silicon, tungsten, boron, bismuth, chromium, lanthanum, barium, antimony, iron, zirconium, tellurium and It represents at least one element selected from the group consisting of cerium, a, b, c, d, e, f and h represent the atomic ratio of each element, g represents the number of ammonium group molecules, and b = 12. When a=0.5~3, c=0.01
~3, d=0.01~2, e=0.01~2, f=0~
5, and h is the number of oxygen atoms necessary to satisfy the valence of each component, and g = 0.01 to 2. Method described.